Simple molecules on a zeolite acceptor center: A quantum-chemical approach

The effectiveness and reliability of the cluster approach to modeling the interaction of several simple molecules (CO, water, ammonia, ethylene, and methanol) with zeolite acceptor centers was shown on the basis of various quantum-chemical methods and a comparison with the data of direct measurements. The Al···CO bonds were found to form in the complex of CO with three-coordinate aluminum. This allows the CO molecule to be used as a test for the acceptor properties of zeolites. A comparison of the calculation results and experimental data on the interaction of one to three RH-type molecules with a zeolite fragment led us to conclude that water, ammonia, ethylene, and methanol acquired proton-donor properties in the field of zeolite acceptor centers. These properties were similar to those of bridge OH groups in hydrogen zeolite forms. Probable schemes of catalysis on zeolites should be constructed taking into account the possible participation of acceptor centers in the conversions of molecules of the type specified.